We consider explicit models. The first example is the nonlinear SSH model[1]}, [2]}, [3]}, [4]}, where \(M_{nm}\)  is given by
\(M_{nm}=-\delta _{nm}\left( t_{A}+t_{B}\right) +\left( t_{A}\delta _{n,2m-1}+t_{B}\delta _{2n,2m+1}\right) \) 
